RESUMEN
Desferrioxamine B (DFOB) is a siderophore native to Streptomyces pilosus biosynthesised by the DesABCD enzyme cluster as a high affinity Fe(III) chelator. Although DFOB has a long clinical history for the treatment of chronic iron overload, limitations encourage the development of new analogues. This review describes a recent body of work that has used precursor-directed biosynthesis (PDB) to access new DFOB analogues. PDB exploits the native biosynthetic machinery of a producing organism in culture medium augmented with non-native substrates that compete against native substrates during metabolite assembly. The method allows access to analogues of natural products using benign methods, compared to multistep organic synthesis. The disadvantages of PDB are the production of metabolites in low yield and the need to purify complex mixtures. Streptomyces pilosus medium was supplemented with different types of non-native diamine substrates to compete against native 1,5-diaminopentane to generate DFOB analogues containing alkene bonds, fluorine atoms, ether or thioether functional groups, or a disulfide bond. All analogues retained function as Fe(III) chelators and have properties that could broaden the utility of DFOB. These PDB studies have also added knowledge to the understanding of DFOB biosynthesis.
Asunto(s)
Deferoxamina/metabolismo , Quelantes del Hierro/metabolismo , Streptomyces/química , Deferoxamina/análogos & derivados , Deferoxamina/química , Quelantes del Hierro/química , Estructura Molecular , Streptomyces/metabolismoRESUMEN
BACKGROUND: A training programme was developed and delivered to a cohort of volunteers who were preparing for a unique role to provide companionship to dying patients in the acute hospital setting. This comprehensive programme aimed to provide an opportunity for participants to fully understand the nature and responsibilities of the role, whilst also allowing sufficient time to assess the qualities and competencies of participants for their ongoing volunteering role. Participants completed reflective diaries throughout the training course to record their ongoing thoughts and feelings. The purpose of this paper is to present a phenomenological analysis of these entries to understand participants' experiences, perceptions and motivations. METHOD: The wider study was structured into three phases. Phase 1 was the delivery of a 12 week, bespoke training programme; Phase 2 involved a 26 week pilot implementation of the Care of the Dying Volunteer Service and Phase 3 was the research evaluation of the training and implementation which would inform the further development of the training programme. Self-reflection is a common component of End of Life training programmes and volunteers in this study completed a reflective diary after participation in each of the training sessions. A thematic analysis was undertaken to explore and understand the participants' experience, perceptions and motivations in relation to their participation in the training. RESULTS: All 19 volunteers completed the reflective diaries. From a potential 228 diary entries over the 12 week training programme, 178 diary entries were submitted (78 %). The following key themes were identified: Dying Alone and the importance of being present, Personal loss and the reconstruction of meaning, Self-Awareness and Personal growth, Self-preservation and Coping strategies and group unity/cohesion. CONCLUSIONS: The participants in this study demonstrated that they were able to use the diaries as an appropriate medium for reflection. Their reflections were also instrumental in the ongoing revision and development of the training programme. Analysis of their entries illustrated that the diaries could provide the opportunity for a reappraisal of their world view and personal philosophy around death and dying. Further research is undoubtedly required, however this paper suggests that self-reflection in this way, supports preparation in honing the appropriate attitudes and qualities required to work in this role.
Asunto(s)
Amigos/psicología , Autoinforme , Cuidado Terminal/métodos , Cuidado Terminal/psicología , Voluntarios/psicología , Educación/métodos , Femenino , Humanos , Masculino , Investigación CualitativaRESUMEN
Traumatic brain injuries (TBIs) may increase the risk for Alzheimer's disease (AD) and its neuropathological correlates, although the mechanisms of this relationship are unclear. The current study examined the synergistic effects of TBI and genetic risk for AD on ß-amyloid (Aß) levels among Vietnam War Veterans. We hypothesized that the combination of TBI and higher polygenic risk score (PRS) for AD would be associated with lower cerebrospinal fluid (CSF) Aß42/40. Data were obtained from the Department of Defense Alzheimer's Disease Neuroimaging Initiative. Participants included Vietnam War Veterans without dementia who identified as White non-Hispanic/Latino and had available demographic, clinical assessment, genetic, and CSF biomarker data. Lifetime TBI history was assessed using The Ohio State University TBI Identification Method. Participants were categorized into those with and without TBI. Among those with a prior TBI, injury severity was defined as either mild or moderate/severe. CSF Aß42/40 ratios were calculated. Genetic propensity for AD was assessed using PRSs. Hierarchical linear regression models examined the interactive effects of TBI and PRS for AD on Aß42/40. Exploratory analyses examined the interaction between TBI severity and PRS. The final sample included 88 male Vietnam War Veterans who identified as White non-Hispanic/Latino (M age = 68.3 years), 49 of whom reported a prior TBI. There was a significant interaction between TBI and PRS, such that individuals with TBI and higher PRS for AD had lower Aß42/40 (B = -0.45, 95% CI: -0.86 to -0.05, p = 0.03). This relationship may be stronger with increasing TBI severity (p = 0.05). Overall, TBI was associated with lower Aß42/40, indicating greater amyloid deposition in the brain, in the context of greater polygenic risk for AD. These findings highlight who may be at increased risk for AD neuropathology following TBI.
RESUMEN
Siderophores are low-molecular-weight organic bacterial and fungal secondary metabolites that form high affinity complexes with Fe(III). These Fe(III)-siderophore complexes are part of the siderophore-mediated Fe(III) uptake mechanism, which is the most widespread strategy used by microbes to access sufficient iron for growth. Microbial competition for limited iron is met by biosynthetic gene clusters that encode for the biosynthesis of siderophores with variable molecular scaffolds and iron binding motifs. Some classes of siderophores have well understood biosynthetic pathways, which opens opportunities to further expand structural and property diversity using precursor-directed biosynthesis (PDB). PDB involves augmenting culture medium with non-native substrates to compete against native substrates during metabolite assembly. This chapter provides background information and technical details of conducting a PDB experiment towards producing a range of different analogues of the archetypal hydroxamic acid siderophore desferrioxamine B. This includes processes to semi-purify the culture supernatant and the use of liquid chromatography-tandem mass spectrometry for downstream analysis of analogues and groups of constitutional isomers.
Asunto(s)
Sideróforos , Sideróforos/biosíntesis , Sideróforos/química , Sideróforos/metabolismo , Espectrometría de Masas en Tándem/métodos , Deferoxamina/metabolismo , Deferoxamina/química , Cromatografía Liquida/métodos , Vías Biosintéticas , Familia de Multigenes , Hierro/metabolismo , Hierro/química , Medios de Cultivo/química , Medios de Cultivo/metabolismoRESUMEN
Chronic stress is a risk factor for dementia but whether it explains unique variance in cognitive decline in older adults above Alzheimer's disease (AD) biomarkers is unknown. In a preclinical cohort of Vietnam Veterans, we examined the relationship between posttraumatic stress disorder (PTSD) symptom severity, AD biomarkers of beta-amyloid (Aß) and tau, and change in cognitive performance on two widely-used screeners, the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). Analyses indicated that PTSD symptom severity was associated with a greater decline on the MMSE (p < 0.04) and MoCA (p < 0.024) after adjusting for biomarkers of AD, notably on the attention scale of the MoCA and the memory index of the MMSE. These analyses survived multiple comparison corrections. Taken together, PTSD symptom severity is associated with accelerated cognitive decline. Treating PTSD should be considered instrumental to maintaining cognitive function as adults age.
Asunto(s)
Enfermedad de Alzheimer , Disfunción Cognitiva , Trastornos por Estrés Postraumático , Veteranos , Humanos , Anciano , Enfermedad de Alzheimer/diagnóstico , Enfermedad de Alzheimer/psicología , Trastornos por Estrés Postraumático/complicaciones , Disfunción Cognitiva/diagnóstico , Disfunción Cognitiva/etiología , Disfunción Cognitiva/psicología , Péptidos beta-Amiloides , Biomarcadores , Proteínas tauRESUMEN
Background: There is a broad and diverse range of symptoms after a concussion, from irritability to nausea. This heterogeneity of symptoms is a challenge for clinicians managing the different presentations among injuries. Prior research has investigated the structure of postconcussive symptoms to determine if they can be grouped into clusters of related symptoms. Purpose/Hypothesis: The purpose of this study was to identify symptom clusters during the acute phase after a sports-related concussion using exploratory factor analysis and to understand the relationship between risk factors for postconcussion symptoms (ie, demographics, injury characteristics, mental health, and sleep qualities) and different symptom clusters. We hypothesized that certain factors would be predictive of specific symptom clusters. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Collegiate athletes (N = 1104) from the Concussion, Assessment, Research, and Education (CARE) Consortium completed the Sport Concussion Assessment Tool-Third Edition symptom assessment tool 24 to 48 hours after concussion. Exploratory factor analysis was conducted on the symptom evaluation to determine symptom clusters 24 to 48 hours after concussion. Regression analysis was used to examine the effects of pre- and postinjury characteristics. Results: Exploratory factor analysis revealed a 4-cluster structure for acute postconcussive symptoms that explained 62% of the variance in symptom reporting: vestibular-cognitive, migrainous, cognitive fatigue, and affective. Delayed reporting, less sleep before assessment, female sex, and being hurt outside of competition (during practice/training) was correlated with increased symptoms for 4 symptom clusters. Depression predicted higher vestibular-cognitive and affective symptoms. Amnesia was correlated with higher vestibular-cognitive and migrainous symptoms, whereas migraine history was associated with more migrainous and affective symptoms. Conclusion: Symptoms can be grouped into 1 of 4 distinct clusters. Certain variables were associated with increased symptoms across multiple clusters and may be indicative of greater injury severity. Other factors (ie, migraine history, depression, amnesia) were associated with a more specific symptom presentation and may be mechanistically related to concussion outcomes and biological markers.
RESUMEN
Biosynthesis of the hydroxamic acid siderophore desferrioxamine D1 (DFOD1, 6), which is the N-acetylated analogue of desferrioxamine B (DFOB, 5), has been delineated. Enzyme-independent Ac-CoA-mediated N-acetylation of 5 produced 6, in addition to three constitutional isomers containing an N-O-acetyl group installed at either one of the three hydroxamic acid groups of 5. The formation of N-Ac-DFOB (DFOD1, 6) and the composite of N-O-acetylated isomers N-O-Ac-DFOB[001] (6a), N-O-Ac-DFOB[010] (6b), and N-O-Ac-DFOB[100] (6c) (defined as the N-O-Ac motif positioned within the terminal amine, internal, or N-acetylated region of 5, respectively), was pH-dependent, with 6a-6c dominant at pH < 8.5 and 6 dominant at pH > 8.5. The trend in the pH dependence was consistent with the pKa values of the NH3+ (pKa â¼ 10) and N-OH (pKa â¼ 8.5-9) groups in 5. The N- and N-O-acetyl motifs can be conceived as a post-biosynthetic modification (PBM) of a nonproteinaceous secondary metabolite, akin to a post-translational modification (PTM) of a protein. The pH-labile N-O-acetyl group could act as a reversible switch to modulate the properties and functions of secondary metabolites, including hydroxamic acid siderophores. An alternative (most likely minor) biosynthetic pathway for 6 showed that the nonribosomal peptide synthetase-independent siderophore synthetase DesD was competent in condensing N'-acetyl-N-succinyl-N-hydroxy-1,5-diaminopentane (N'-Ac-SHDP, 7) with the dimeric hydroxamic acid precursor (AHDP-SHDP, 4) native to 5 biosynthesis to generate 6. The strategy of diversifying protein structure and function using PTMs could be paralleled in secondary metabolites with the use of PBMs.
Asunto(s)
Deferoxamina , Sideróforos , Acetilcoenzima A/metabolismo , Vías Biosintéticas , Deferoxamina/metabolismo , Concentración de Iones de Hidrógeno , Sideróforos/metabolismoRESUMEN
Neural oscillations, or brain rhythms, fluctuate in a manner reflecting ongoing behavior. Whether these fluctuations are instrumental or epiphenomenal to the behavior remains elusive. Attempts to experimentally manipulate neural oscillations exogenously using noninvasive brain stimulation have shown some promise, but difficulty with tailoring stimulation parameters to individuals has hindered progress in this field. We demonstrate here using electroencephalography (EEG) neurofeedback in a brain-computer interface that human participants (n = 44) learned over multiple sessions across a 6-day period to self-regulate their Beta rhythm (13-20 Hz), either up or down, over the right inferior frontal cortex. Training to downregulate Beta was more effective than training to upregulate Beta. The modulation was evident only during neurofeedback task performance but did not lead to offline alteration of Beta rhythm characteristics at rest, nor to changes in subsequent cognitive behavior. Likewise, a control group (n = 38) who underwent training to up or downregulate the Alpha rhythm (8-12 Hz) did not exhibit behavioral changes. Although the right frontal Beta rhythm has been repeatedly implicated as a key component of the brain's inhibitory control system, the present data suggest that its manipulation offline prior to cognitive task performance does not result in behavioral change in healthy individuals. Whether this form of neurofeedback training could serve as a useful therapeutic target for disorders with dysfunctional inhibitory control as their basis remains to be tested in a context where performance is abnormally poor and neural dynamics are different.
Asunto(s)
Interfaces Cerebro-Computador , Neurorretroalimentación , Autocontrol , Ritmo alfa/fisiología , Ritmo beta/fisiología , Encéfalo/fisiología , Electroencefalografía , HumanosRESUMEN
BACKGROUND: University students have high rates of pharyngeal carriage of Neisseria meningitidis. Interruption of carriage acquisition is an important mechanism of vaccines for inducing herd protection. 4CMenB and MenACWY-CRM vaccines have been shown to be immunogenic against meningococcal serogroups B and ACWY respectively in younger age groups, and also to elicit a modest impact on meningococcal carriage in vaccinated students. However, vaccine responses in university students and the impact of serum bactericidal antibody (SBA) titers on meningococcal carriage are undetermined. METHODS: Immunogenicity of two 4CMenB doses or one MenACWY-CRM dose was measured in university students at Months 2, 4, 6 and 12 post-first vaccination. Immunogenicity of one MenACWY-CRM dose in students with previous meningococcal serogroup C conjugate vaccination was also assessed. Immune responses were measured with an SBA assay using human complement (hSBA) against three reference strains for serogroup B and against one strain for each for serogroups C and Y. Correlations between hSBA titers and meningococcal carriage were analyzed. RESULTS: All subjects demonstrated robust functional antibody responses to both vaccines at Month 2 and a high proportion maintained protective hSBA titers up to Month 12. At baseline, carriage of disease-associated serogroup B strains and serogroups C and Y were higher in subjects with already-protective hSBA titers. Post-vaccination, while both 4CMenB and MenACWY-CRM elicited robust immunogenicity in students, significant correlations between post-vaccination hSBA titers and carriage of disease-associated serogroups were not observed. CONCLUSIONS: 4CMenB and MenACWY-CRM were both highly immunogenic. There was no correlation between carriage and post-vaccination hSBA titers.